Shipping container for radioactive material

Abstract: A shipping container (10) for highly enriched uranium includes a heavy duty drum (20) containing insulation material (22), the drum (20) forming an outer container. Fibreboard and plywood form the insulation material (22), and are shaped and sized to closely receive an inner container (14) formed from stainless steel. The inner container (14) has a closure lid that is bolted on and forms a seal through the use of O-rings.

Description: The present invention generally relates to shipping containers for radioactive material such as unirradiated highly enriched uranium. Shipping containers previously used for shipping unirradiated highly enriched uranium were designed to meet the requirements of the US standard 10 CFR 71 as it existed before incorporation of new international standards (IAEA Safety Series 6, 1985 Edition). Containers that were used to meet the prior standards are typically steel containers with a threaded closure, with the steel container being centred in a steel shipping drum and isolated from the drum wall with fibreboard. These containers do not meet recent changes in NRC and IAEA (International Atomic Energy Agency) standards. This leaves a need for shipping containers that meet the new standards. According to the present invention there is provided a shipping container for highly enriched uranium or the like, the container comprising: a heavy duty drum; insulation material received inside said drum, comprising a first layer of fibreboard sized to be received in said drum and positioned across the bottom of said drum, a first layer of plywood sized to be received in said drum and positioned across the top of said first layer of fibreboard, a fibreboard cylinder open at each end and sized to be received inside said drum, a second layer of plywood sized to be received in said drum and positioned on top of said fibreboard cylinder, and a second layer of fibreboard sized to be received in said drum and positioned across the top of said second layer of plywood; an inner container having one open end and sized to be received in said fibreboard cylinder, said inner container being provided with a test port; a closure lid sized to be received on said inner container; means for attaching said closure lid to said inner container and forming a seal therebetween; and a cover sized to be received on said heavy duty drum. A preferred embodiment of the present invention provides a shipping container for highly enriched uranium that can meet the new international standards. The outer container has insulators of fibreboard and plywood in a heavy duty drum that meets current NRC (10 CFR 71) and IAEA (Safety Series No. 6, 1985 Edition) standards. A drum that meets DOT standards 17C has a fibreboard and plywood liner that provides thermal insulation, impact protection, and axial support to the inner container. The inner container is formed from stainless steel and has a closure lid that forms a seal with the inner container to prevent leakage. The cover on the drum is closed using a heavy duty clamp ring with a bolt having a tamper proof seal. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: Figure 1 is a side-sectional partial broken-away view of an embodiment of the invention; and Figure 2 is a side-sectional view of the inner container shown in Figure 1. Referring to the drawings, a shipping container 10 generally comprises an outer container 12, an inner container 14, a closure lid 40 for the inner container 14, and means 18 for attaching the closure lid 40 to the inner container 14 and for forming a seal therebetween. As seen in Figure 1, the outer container 12 is formed from a 0.2 m 3 (fifty-five gallon) heavy duty drum 20 that meets U.S. DOT (United States Department of Transportation) specification 17C and insulation material 22 formed from fibreboard and fire retardant plywood. A first layer 24 of fibreboard is sized to be received and positioned across the bottom of the drum 20. A first layer 26 of plywood is sized to be received in the drum 20 and is positioned across the top of the first fibreboard layer 24. A fibreboard cylinder 28 is open at both ends and sized to be received in the drum 20. The inner dimensions of the fibreboard cylinder 28 are sized to closely receive the inner container 14. A second layer 30 of plywood is sized to be received in the drum 20 and is positioned on top of the fibreboard cylinder 28. A second layer 32 of fibreboard is sized to be received in the drum 20 and is positioned across the top of the second plywood layer 30. A cover 34 is provided for the drum 20 to secure the contents inside. The inner container 14, seen in Figure 2, has one open end and is preferably formed from stainless steel such as austenitic stainless steel schedule 40S pipe (seamless or welded), and is sized to be received inside the fibreboard cylinder 28 inside the drum 20. The closed end of the inner container 14 may be a flat bottom cap machined from plate and welded to the pipe. In the preferred embodiment, the inner dimensions of the inner container 14 are a 125 mm (five inch) diameter and 560 mm (twenty-two inches) length. This has been calculated as the largest volume possible for the transport of one hundred percent enriched (highly enriched) uranium while still being critically safe in the event of the ingress of water into the inner container 14. The open end of the inner container 14 is provided with a flange 38. A test port 36 is provided in the closure lid 40 to allow testing for every shipment. The closure lid 40 is sized to be received at the open end of the inner container 14. The means 18 for attaching the lid 40 to the inner container 14 and forming a seal therebetween is provided in the form of O-rings 42, O-ring grooves 44 on the lid 40, threaded bores 46 in the flange 38, corresponding bores 48 through the lid 40, and bolts 50. In the preferred embodiment, eight threaded bores 46 are spaced around the circumference of the flange 38 and the corresponding bores 48 are provided through the lid 40 to allow the lid 40 to be bolted to the inner container 14. The closure lid 40 is provided with a shear lip 41 that extends 3.2 mm (0.125 inch) into the inner container 14. The shear lip 41 centres the lid 40 on the inner container 14 and prevents any shear load from being transmitted to and through the bolts 50. In the preferred embodiment, at least two sets of O-ring grooves 44 are provided on the lid 40. The O-rings 42 are received in the grooves 44 such that a seal is formed between the lid 40 and the inner container 14 when the lid 40 is bolted to the inner container 14. The test port 36 is formed by a port through the lid 40 that is located between the O-rings 42 and allows testing to determine if there is any leakage once the lid 40 has been bolted to the inner container 14. The innermost O-ring forms the primary seal. A handling bail 52 is provided on the lid 40 to allow remote handling of the inner container 14 for loading into or out of the outer container 12. In operation, highly enriched uranium that may be in the form of solids, pellets, powder, crystals, or liquid solutions is loaded into the inner container 14 and the lid 40 is positioned on the inner container 14 and bolted into place such that pressure on the O-rings 42 creates a seal between the lid 40 and the inner container 14. Flat washers 54 placed between the bolt heads and the closure lid 40 are then bent upwards to ensure that the bolts 50 are not loosened during transport. Remote heavy lifting equipment may then be attached to the lifting bail 52 for lifting and positioning the inner container 14 in the outer container 12 which has been lined with the first layers of fibreboard and plywood 24, 26, and with the fibreboard cylinder 28. The second layers of plywood and fibreboard 30, 32 are then placed over the inner container 14. The inner container 14 and the insulation material 22 are sized such that the maximum radial clearance between the inner container 14 and the insulation material 22 and between the insulation material 22 and the drum 20 is 6.4 mm (one-fourth inch). The cover 34 is then secured on the drum 20 and the shipping container 10 is ready for shipping. As indicated in NRC docket 71-9250, the shipping container 10 has been analyzed and tested and deemed to conform to the most recent NRC and IAEA standards for shipping containers for highly enriched uranium. The inner container 14 is fabricated in accordance with ASME Code Section III (Subsection NB-4000), NUREG/CR-3019 (Category I), and NUREG/CR-3854 (Category I). The mating faces of the flange 38 and the closure lid 40 are machined flat to within 0.05 mm (0.002 inches), and the face seal surfaces are finished to 16 RMS. The test port 36 is plugged during shipment. Because many differing embodiments may be made within the scope of the inventive concept herein taught and defined in the claims, and because many modifications may be made in the embodiment herein detailed in accordance with the description, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.

Claims: A shipping container for highly enriched uranium or the like, the container comprising: a heavy duty drum (20); insulation material (22) received inside said drum (20), comprising a first layer (24) of fibreboard sized to be received in said drum (20) and positioned across the bottom of said drum (20), a first layer (26) of plywood sized to be received in said drum (20) and positioned across the top of said first layer (24) of fibreboard, a fibreboard cylinder (28) open at each end and sized to be received inside said drum (20), a second layer (30) of plywood sized to be received in said drum (20) and positioned on top of said fibreboard cylinder (28), and a second layer (32) of fibreboard sized to be received in said drum (20) and positioned across the top of said second layer (30) of plywood; an inner container (14) having one open end and sized to be received in said fibreboard cylinder (28), said inner container (14) being provided with a test port (36); a closure lid (40) sized to be received on said inner container (14); means (18) for attaching said closure lid (40) to said inner container (14) and forming a seal therebetween; and a cover (34) sized to be received on said heavy duty drum (20). A shipping container according to claim 1, comprising a handling bail (52) on said inner container (14). A shipping container according to claim 1 or claim 2, wherein said inner container (14) is formed from austenitic stainless steel. A shipping container according to claim 1, claim 2 or claim 3, wherein said means (18) for attaching said closure lid (40) to said inner container (14) and forming a seal therebetween comprises: means (50) for bolting said closure lid (40) to said inner container (14); and at least one O-ring (42) received in a groove (44) on said closure lid (40). A shipping container according to any one of the preceding claims, comprising a test port (36) provided in said closure lid (40). A shipping container according to any one of the preceding claims, wherein said means (18) for attaching said closure lid (40) to said inner container (14) and forming a seal therebetween includes two O-rings (42) received in separate grooves (44) in said closure lid (40). A shipping container according to claim 6, wherein said test port (36) is located between said O-rings (42). A shipping container according to any one of the preceding claims, wherein said closure lid (40) is provided with a shear lip (41).

Inventors: CHILDRESS PAUL CHARLES, CHILDRESS, PAUL CHARLES
Applicants: BABCOCK & WILCOX CO, THE BABCOCK & WILCOX COMPANY
Application year: 1994
Main classification: G21F5
IPC codes: G21F5